Urban trees provide numerous ecosystem services in cities such as pollution absorption and reduced urban heat island intensity, energy use, and mental fatigue. Understanding urban tree species diversity can enhance tree planning and management in rapidly urbanizing areas. However, few studies have examined the effects of urbanization on urban tree diversity in Thailand. This study assessed the diversity of large trees in urban landscapes including 11 cities along the 372 km Chao Phraya River Rim in central Thailand. Species diversity, importance value, and distribution were evaluated in each city. Our survey documented 987 large trees belonging to 65 species, 48 genera, and 31 families. The dominant species of Dipterocarpus alatus and Hopea odorata had the highest importance and relative abundance. The highest abundance of large trees was seen in the rural city of Sing Buri, while large urban cities such as Ayutthaya and Bangkok exhibited the highest species diversity. Detrended correspondence analysis indicated that the diversity of unique species was high in large urban cities, while dominant and common species were ubiquitous in rural cities. These findings suggest that large trees are few in number but exhibit high species diversity in large rapidly urbanizing cities. Therefore, preserving good site conditions is critical for the survival of large trees in urban cities. Heritage tree registration may aid preservation efforts and enhance the benefits of these large trees in rapidly urbanizing areas.

This study aimed to investigate the physical factors influencing the occurrence of forest fires and to create a fire risk map of Phrae Province. Remote sensing and geographic information system (GIS) technology were applied for the analysis, focusing on seven factors: the digital elevation model (DEM); slope; Normalized Difference Vegetation Index (NDVI); aspect; and distances from people, water, and roads. All of these geographical factors can affect forest fires. This resulted in a MaxEnt (Maximum Entropy) model with an AUC (area under the curve) of 0.849, indicating its great prediction ability. The findings revealed that the variables influencing forest fire incidence were the DEM, NDVI, slope, distance from roads, distance from water, distance from communities, and aspect, in that order. Subsequently, a fire risk map for wildfires was developed by reclassifying the data into five levels—very low risk, low risk, medium risk, high risk, and very high risk—accounting for 341,395.54, 88,132.64, 76,162.41, 81,157.55, and 57,384.10 hectares or 52.99, 13.68, 11.82, 12.60, and 8.91% of the total area, respectively. The areas classified as very high risk, high risk, medium risk, and low risk included the Song, Long, and Rong Kwang Districts. The area with the lowest risk was Nong Muang Khai District.

Studies of carbon storage using functional traits have shown that it is strongly affected by functional diversity. We explored the effects of functional diversity on carbon storage at the edge of a deciduous dipterocarp forest (DDF) ecosystem in Thailand. Aboveground biomass carbon (AGBC), soil organic carbon (SOC), and total ecosystem carbon (TEC) were used as indicators of carbon storage. Five functional traits were measured in 49 plant species to calculate the community-weighted mean (CWM) and Rao’s quadratic diversity (FQ). We assessed which functional diversity metrics best-explained carbon storage. The results indicated that AGBC had a significant, positive relationship with the FQ of wood density, and a negative relationship with the CWM of leaf thickness. SOC had a significant, negative association with the FQ of leaf thickness and a positive relationship with the CWM of specific leaf area (SLA). TEC was best predicted by increases in the FQ of wood density and the CWM of SLA. These findings indicate that CWM and FQ are important for understanding how plant traits influence carbon storage in DDF edge ecosystems and suggest that promoting a high diversity of species with dissimilar wood density and high SLA may increase carbon storage in chronically disturbed DDF ecosystems.

Asanok L, Kamyo T, Marod D. 2020. Maximum entropy modeling for the conservation of Hopea odorata in riparian forests, central Thailand. Biodiversitas 21: 4663-4670. Hopea odorata plays a dominant role in both ecologically and economically in Thailand. We analyzed potentially suitable areas for H. odorata in the riparian zone of the Chao Phraya River using the software MaxEnt. Modeling included 164 occurrence records along with 19 climate-related variables, slope, aspect, and elevation. Precipitation was the key climatic variable influencing the distribution of H. odorata. Riparian areas along the Chao Phraya that were predicted to be highly suitable for this species were located in the provinces of Nakhon Sawan, Ang Thong, Phra Nakhon Si Ayutthaya, Pathum Thani, Nonthaburi, and Bangkok. The ROC AUC score was 0.891, indicating that MaxEnt is an excellent tool for predicting suitable regions for the restoration or cultivation of commercially and ecologically valuable species such as H. odorata. Models such as what we have presented here can facilitate habitat conservation and sustainable resource use for rare and important plants.

Evaluating potential (PES) and realized (RES) ecosystem services can significantly improve the clarity and understanding of sustainable natural resource management practices. This study determined spatial distribution indices and assessed the economic value of both PES and RES in Northern Thailand. The geographic distribution and intensity of 17 ecological services of six land use categories (i.e., forests, agriculture, shrubland, urban land, water bodies, and barren land) were estimated for the distribution and unit values of PES and RES, by using the Co$ting Nature Model. Our results suggested that the PES and RES values were spatially consistent. The map showing the distribution of PES and RES values revealed high values in the cities of Chiang Mai, Chiang Rai, Lamphun, Lampang, Phitsanulok, and Nakhon Sawan. Nutrient cycling, soil formation, and water supply were identified as the top potential ecological services, while nutrient cycling, water supply, and soil formation were the most realized. The ecosystem service packages in Northern Thailand had a potential annual value of 36.31 billion USD per year. However, after adjusting for relative indices, the realized ecosystem services were valued at 13.44 billion USD per year, representing only one-third of the potential value. To manage resources effectively and make informed decisions, it is essential to comprehend the gap between possible and actual ecosystem services. This research underscores the financial worth of ecosystem services and emphasizes the significance of using them sustainably to enhance human well-being and conserve the environment in Northern Thailand.

The natural suitability of teak (Tectona grandis L.f.) at Mae Yom National Park, Phrae Province, Thailand was investigated using logistic regression. The study identified the relationship between key physical and soil properties with the presence of teak at natural sites, and applied a geographic information system platform to identify potential natural sites of teak. Fourteen variables were included in the model, five of these were found to have a significant effect (p < 0.05). Elevation was the most significant topographic variable, whereas magnesium, organic matter, potassium, and calcium were the most significant soil variables. The site prediction had 91.8% accuracy for identifying areas with high, moderate, and low probabilities of being suitable natural habitats for teak. These areas covered 87.63, 244.33, and 163.54 km2, respectively.